libs/random/example/die.cpp

// die.cpp
//
// Copyright (c) 2009
// Steven Watanabe
//
// Distributed under the Boost Software License, Version 1.0. (See
// accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
//[die
/*`
For the source of this example see
[@boost://libs/random/example/die.cpp die.cpp].
First we include the headers we need for __mt19937
and __uniform_int_distribution.
*/
#include <boost/random/mersenne_twister.hpp>
#include <boost/random/uniform_int_distribution.hpp>
/*`
We use __mt19937 with the default seed as a source of
randomness. The numbers produced will be the same
every time the program is run. One common method to
change this is to seed with the current time (`std::time(0)`
defined in ctime).
*/
boost::random::mt19937 gen;
/*`
[note We are using a /global/ generator object here. This
is important because we don't want to create a new [prng
pseudo-random number generator] at every call]
*/
/*`
Now we can define a function that simulates an ordinary
six-sided die.
*/
int roll_die() {
/*<< __mt19937 produces integers in the range [0, 2[sup 32]-1].
However, we want numbers in the range [1, 6]. The distribution
__uniform_int_distribution performs this transformation.
[warning Contrary to common C++ usage __uniform_int_distribution
does not take a /half-open range/. Instead it takes a /closed range/.
Given the parameters 1 and 6, __uniform_int_distribution can
can produce any of the values 1, 2, 3, 4, 5, or 6.]
>>*/
boost::random::uniform_int_distribution<> dist(1, 6);
/*<< A distribution is a function object. We generate a random
number by calling `dist` with the generator.
>>*/
return dist(gen);
}
//]
#include <iostream>
int main() {
for(int i = 0; i < 10; ++i) {
std::cout << roll_die() << std::endl;
}
}